Criminology has not systematically identified the cause or causes of perhaps the most seminal event in crime and justice of the last half century: the crime decline of the 1990s. This paper uses a causes-of-effects analysis to infer the mechanisms of the crime decline. This is not a purely academic exercise—there has been a large increase in violence, particularly gun violence at the beginning of the 2020s. Identifying the mechanisms of the last crime decline can inform the development of contemporary strategies. Here, two classes of crime decline causes are proposed: mechanisms that are endogenous to the criminal law system and mechanisms that are exogenous to it. The latter class includes impacts of changes in macroeconomics, consumer behavior, and public interest policy where positive externalities that arose from those factors contributed to the crime decline. A descriptive effect of causes analysis suggests that these exogenous mechanisms contributed disproportionately to the crime decline as compared to endogenous mechanisms. Further, consumer behavior and public interest externalities are well aligned with potential policy levers and particularly salient to current and future efforts to reduce crime and violence prospectively. The analysis suggests that efforts to improve public safety require policies that fall outside of traditional criminal justice approaches.

犯罪学尚未系统地确定可能是过去半个世纪犯罪和司法领域最具开创性事件的一个或多个原因：1990 年代的犯罪率下降。本文使用因果分析来推断犯罪下降的机制。这不是纯粹的学术活动——暴力事件大幅增加，尤其是 2020 年代初的枪支暴力事件。确定上次犯罪率下降的机制可以为当代战略的发展提供信息。在这里，提出了两类犯罪下降的原因：刑法制度的内生机制和外生机制。后一类包括宏观经济、消费者行为变化的影响，和公共利益政策，其中由这些因素引起的正外部性导致犯罪率下降。原因分析的描述性效果表明，与内生机制相比，这些外生机制对犯罪率下降的贡献不成比例。此外，消费者行为和公共利益的外部性与潜在的政策杠杆非常一致，对于当前和未来未来减少犯罪和暴力的努力尤其重要。分析表明，改善公共安全的努力需要超出传统刑事司法方法的政策。消费者行为和公共利益的外部性与潜在的政策杠杆非常一致，对于当前和未来未来减少犯罪和暴力的努力尤其重要。分析表明，改善公共安全的努力需要超出传统刑事司法方法的政策。消费者行为和公共利益的外部性与潜在的政策杠杆非常一致，对于当前和未来未来减少犯罪和暴力的努力尤其重要。分析表明，改善公共安全的努力需要超出传统刑事司法方法的政策。